Although the holddown device of this invention has general utility, it is designed primarily to clamp a car body on a carrier which moves through a cleaner dip tank and a primer dip tank before the car body is painted. The carrier must be lowered into and raised from each dip tank and it may also be tilted one way and another. One or more clamps are provided to secure the car body to the carrier. The car body must be securely clamped, and the clamps must not fail, yet they should be easy to operate.
In the specific embodiment about to be described, a clamp arm is pivoted to a base for movement between a retracted position and a clamping position. The clamp arm has a hook end extending outwardly from the pivot, and a tail extending outwardly from the pivot at an acute angle to the hook end. A cam is pivoted to the base beneath the hook arm and has a camming periphery engageable with the tail of the clamp arm. The cam is rotatable in one direction to a locking position and in the opposite direction to a release position. When the cam is rotated to its locking position, it swings the clamp arm to its clamping position. A link interconnects the tail of the clamp arm and the cam. When the cam is rotated to its release position, the link returns the clamp arm to its retracted position.
When the cam rotates the clamp arm to its clamping position, there is a reaction force against the cam. The shape of the cam periphery and the tail of the clamp arm at the point of contact are such that the reaction force has a vector which extends on a straight line through the cam pivot. This insures that the clamp arm is securely locked in its clamping position without any tendency to release.
One object of this invention is to provide a holddown device having the foregoing features and capabilities.
Another object is to provide a holddown device which is constructed of a relatively few simple parts, is rugged and durable in use, and is capable of being inexpensively manufactured and assembled and is easy to operate.